Orthodontic braces comprised of a plurality of brackets and an archwire for applying the appropriate force to a patient's teeth are commonly used to move the teeth into a desired configuration or alignment. Each bracket is firmly attached to a respective tooth and serves as a handle on the tooth for the force-producing archwire. The forces applied by the archwires through the brackets are gradually adjusted by the dentist to move and/or re-orient each tooth in a desired manner. These forces applied to the teeth move the teeth gradually toward the positions and/or orientations desired by the orthodontist. Different bracket arrangements are available to the dentist, with the dentist generally selecting a particular bracket system based upon the patient's specific pre-treatment malocclusion (condition requiring treatment), dental surface morphology, and facial type. However, the various bracket systems are not custom designed for each tooth, nor are they configured for the individual patient's jaw bone relationships or functional movement patterns. Rather, bracket and archwire configurations are of a generally generic design with the teeth in a static position. For example, the slots which hold the wire in the different brackets are substantially uniform. Because of this, the forces of the archwire on the teeth must be adjusted by bending or otherwise distorting the archwires.
The inability to adapt to the individual patient's condition has rendered prior approaches generally time consuming, expensive and of limited precision. For example, it is frequently necessary to replace the brackets attached to the patient's teeth as treatment progresses. In addition, prior approaches have required a considerable amount of work by the orthodontist over an extended period of time to progressively adjust the forces applied against the teeth. Moreover, the bending and distortion of the archwire to adjust the forces on the patient's teeth is largely accomplished on an empirical basis based in substantial part upon the experience of the orthodontist. Even the experienced orthodontist has difficulty in bending and twisting the archwire precisely so that the proper force is applied to the brackets attached to each of the patient's teeth. Moreover, unless the bracket is attached at the proper location on the tooth, precise positioning and alignment of the set of teeth is virtually impossible. Current approaches require the orthodontist to visually select the optimum bracket location and then attempt to locate the bracket accordingly on the tooth. This imprecise "eyeballing" approach limits the degree of alignment of the repositioned teeth and generally ignores functional movement of the mandible (lower jaw).
In an ideally functioning occlusion, certain anatomic structures maintain interactive relationships to each other. For example, as the occlusal plane steepens (gets higher posteriorly), the angulation of the upper incisors becomes more vertical. Other related structures are the cusp angulations of the posterior teeth and the steepness of the articular eminence of the mandibular fossa. All of these relationships can be measured and expressed numerically.
In addition, all of these functional relationships undergo adaptation when the relationships of the upper and lower jaw bones are varied in the anterior-posterior plane. For example, if the lower jaw is too far forward in relation to the upper (Class III), the occlusal plane is lower posteriorly and all the other relationships must change proportionately in order to maintain a smoothly functioning occlusion without traumatic interference. FIGS. 1 and 2 illustrate these relationships. These relationships have been published and are generally accepted knowledge. However, the great variation of individual tooth anatomy and the number of existing variables have precluded such idealization of orthodontic treatment goals.
The present invention addresses the aforementioned limitations of the prior art by allowing the orthodontist not only to allow inclusion of variable tooth anatomy into idealized bracket placement, but also to include for the first time other factors which determine a non-traumatic, properly functioning occlusion for a specific individual. The present invention contemplates an orthodontic bracketing system and method therefor which employs a digital computer as well as a video display for custom designing a set of orthodontic jigs, or positioning fixtures, for engaging each bracket and tooth combination for optimum positioning of the bracket on the tooth for subsequent repositioning and/or reorientation of the tooth by means of an archwire. Digital data of the size, shape and contour of each tooth is measured, recorded and displayed to permit the central axis of each tooth to be viewed by the orthodontist and to be moved in virtual space using torque, tip and angulation values as well as in/out position information to relocate and/or reorient the tooth, as desired. Using the measured and stored digital data representing the size, shape and contour of each tooth, the relationship of the jaw bone and the movement path of the lower jaw, a computer controlled milling machine forms each positioning jig to match its associated tooth to ensure optimum positioning of the orthodontic bracket on the tooth.